In Vitro Antifungal Activity of Micafungin and Caspofungin Against Dermatophytes Isolated from China

Aims

The aims of this study are to investigate the in vitro activities of micafungin and caspofungin that are two new echinocandin antifungal drugs against clinically isolated dermatophytes in China and to define MEC (minimal effective concentration) as the reading endpoints of this study in accordance with (Clinical and laboratory Standards Institute) CLSI M38-A2 reference.

Methods

Minimal effective concentrations (MECs) of micafungin and caspofungin for 82 dermatophyte strains were determined according to CLSI (formerly NCCLS) M38-A2 broth microdilution methods.

Results

(1) The MEC_90s of micafungin for Trichophyton violaceum and Trichophyton tonsurans were 0.25 μg/mL, and for Microsporum canis and Trichophyton verrucosum were 0.06 μg/mL. The MEC_90s for Trichophyton rubrum, Trichophyton mentagrophytes, Microsporum gypseum and Epidermophyton floccosum were 0.03 μg/mL. (2) The MEC_90s of caspofungin for T. rubrum, T. violaceum and T. tonsurans were 1 μg/mL, and for T. mentagrophytes, M. canis, M. gypseum, E. floccosum and T. verrucosum were 0.5 μg/mL. (3) Compared with caspofungin, micafungin demonstrated lower MEC value to dermatophytes (P < 0.05).

Conclusions

Micafungin has stronger in vitro antifungal activity than caspofungin.     

In Vitro Nitrogen Fixation by Two Actinomycete Strains Isolated from Casuarina Nodules

Acetylene reduction activity was demonstrated in pure cultures of two actinomycete strains isolated from nodules of Casuarina equisetifolia. This activity was comparable to that of free-living Rhizobium strains, but appeared to be less sensitive to pO₂ and more sensitive to the presence of combined nitrogen.     

Molecular Identification and Antifungal Susceptibility of Yeasts and Molds Isolated from Patients with Otomycosis

Mycopathologia - Fungal otitis externa, an infection of the external auditory canal caused by molds and yeasts, accounts for approximately 10–20% of ear canal infections accompanying high...     

In Vitro Susceptibility of Environmental Isolates of Exophiala dermatitidis to Five Antifungal Drugs

Several dematiaceous fungi frequently isolated from nature are involved in cases of superficial lesions to lethal cerebral infections. Antifungal susceptibility data on environmental and clinical isolates are still sparse despite the advances in testing methods. The objective of this study was to examine the activities of 5-flucytosine, amphotericin B, itraconazole, voriconazole and terbinafine against environmental isolates of Exophiala strains by minimum inhibition concentration (MIC) determination. The strains were obtained from hydrocarbon-contaminated soil, ant cuticle and fungal pellets from the infrabuccal pocket of attine gynes. Broth microdilution assay using M38-A2 reference methodology for the five antifungal drugs and DNA sequencing for fungal identification were applied. Terbinafine was the most active drug against the tested strains. It was observed that amphotericin B was less effective, notably against Exophiala spinifera, also studied. High MICs of 5-flucytosine against Exophiala dermatitidis occurred. This finding highlights the relevance of studies on the antifungal resistance of these potential opportunistic species. Our results also contribute to a future improvement of the standard methods to access the drug efficacy currently applied to black fungi.     

Molecular Identification and In Vitro Antifungal Susceptibility of Aspergillus Isolates Recovered from Otomycosis Patients in Western China

Mycopathologia - Aspergillus species are the most common causative agents involved in otomycosis. In this study, 45 Aspergillus isolates were obtained from patients with otomycosis in western China...     

Genotyping and Antifungal Drug Susceptibility of Trichosporon asahii Isolated from Chinese Patients

As a major pathogenic agent of trichosporonosis, Trichosporon asahii can cause life-threatening infection in immunocompromised patients. In this study, we analyzed the genotypes of the intergenic spacer (IGS) 1 region of the rRNA gene and the antifungal drug susceptibility of eight T. asahii isolates obtained from Chinese patients. Five genotypes were identified from the eight isolates, including three novel genotypes, three genotype 1, and two genotype 4. The eight T. asahii isolates were resistant to amphotericin B, 5-flucytosine, and terbinafine, but were highly sensitive to fluconazole (FLC), itraconazole (ITC), and voriconazole (VRC). The mean minimum inhibitory concentrations (MICs) of FLC and VRC were significantly lower than those reported in most other countries, while that of ITC was slightly higher. Our results suggest that genotypes of the T. asahii isolated from China are different from those of other countries, and azole drugs appeared to be more effective on the Chinese isolates. These results provide new insights into the epidemiology and antifungal treatment for T. asahii.     

Virulence Factors and Antifungal Susceptibility in Candida Species Isolated from Dermatomycosis Patients

Mycopathologia - Dermatomycoses caused by Candida spp. are increasingly common, however there are few reports in the literature regarding their epidemiology, pathogenesis and antifungal...     

In Vitro Susceptibility of Berberine Combined with Antifungal Agents Against the Yeast Form of Talaromyces marneffei

Mycopathologia - Talaromyces (Penicillium) marneffei can cause fatal disseminated infection in immunocompromised hosts. However, therapeutic strategies for the mycosis are limited. Reports of the...     

In Vitro Cultivation and Antibiotic Susceptibility of a Cytophaga-Like Intracellular Symbiote Isolated from the Tick Ixodes scapularis

A Cytophaga-like organism (CLO), isolated from the tick Ixodes scapularis (IsCLO), was adapted to growth in insect cell lines and its antibiotic sensitivity was tested. IsCLO were introduced to four insect cell lines, and their growth was measured by quantitative polymerase chain reaction. IsCLO propagated well in a mosquito cell line, AeAl-2, and caused cytopathic effects in host cells. A lepidopteran cell line, HZ-AM1, was also suitable for propagation of IsCLO and kept a steady state with bacterial growth. Using IsCLO-infected AeAl-2, antibiotics effective against the bacteria included ampicillin, chloramphenicol, penicillin-G, rifampicin, and tetracycline. These antibiotics will be useful for eliminating CLO from host arthropods, which is necessary for in vivo studies of the intracellular facultative symbiotes.     

Antifungal Efficacy during Candida krusei Infection in Non-Conventional Models Correlates with the Yeast In Vitro Susceptibility Profile

The incidence of opportunistic fungal infections has increased in recent decades due to the growing proportion of immunocompromised patients in our society. Candida krusei has been described as a causative agent of disseminated fungal infections in susceptible patients. Although its prevalence remains low among yeast infections (2–5%), its intrinsic resistance to fluconazole makes this yeast important from epidemiologic aspects. Non mammalian organisms are feasible models to study fungal virulence and drug efficacy. In this work we have used the lepidopteran Galleria mellonella and the nematode Caenorhabditis elegans as models to assess antifungal efficacy during infection by C. krusei. This yeast killed G. mellonella at 25, 30 and 37°C and reduced haemocytic density. Infected larvae melanized in a dose-dependent manner. Fluconazole did not protect against C. krusei infection, in contrast to amphotericin B, voriconazole or caspofungin. However, the doses of these antifungals required to obtain larvae protection were always higher during C. krusei infection than during C. albicans infection. Similar results were found in the model host C. elegans. Our work demonstrates that non mammalian models are useful tools to investigate in vivo antifungal efficacy and virulence of C. krusei.     

In Vitro Antifungal Susceptibility of Oral <Emphasis Type="Italic">Candida</Emphasis> Isolates from Patients Suffering from Caries and Chronic Periodontitis

Caries and chronic periodontitis are common oral diseases where a higher Candida colonization is reported. Antifungal agents could be adjuvant drugs for the therapy of both clinical conditions. The aim of the current study has been to evaluate the in vitro activities of conventional and new antifungal drugs against oral Candida isolates from patients suffering from caries and/or chronic periodontitis. In vitro activities of amphotericin B, fluconazole, itraconazole, miconazole, nystatin, posaconazole and voriconazole against 126 oral Candida isolates (75 Candida albicans, 18 Candida parapsilosis, 11 Candida dubliniensis, six Candida guilliermondii, five Candida lipolytica, five Candida glabrata, four Candida tropicalis and two Candida krusei) from 61 patients were tested by the CLSI M27-A3 method. Most antifungal drugs were highly active, and resistance was observed in less than 5% of tested isolates. Miconazole was the most active antifungal drug, being more than 98% of isolates susceptible. Fluconazole, itraconazole, and the new triazoles, posaconazole and voriconazole, were also very active. Miconazole, fluconazole and voriconazole have excellent in vitro activities against all Candida isolates and could represent suitable treatment for a hypothetically adjunctive therapy of caries and chronic periodontitis.     

Microbiological Characteristics and Susceptibility Patterns of Strains of Rhodotorula Isolated from Clinical Samples

The members of the genus Rhodotorula show a marked ubiquity. In man, they have been isolated from faeces, nails, skin, sputum, digestive tract and adenoids, forming part of the normal human flora, although in recent years cases have been reported of both local and systemic infection by this yeast. There are virtually no studies in the literature on the sensitivity of this genus to the antifungal agents in common clinical use. Therefore, it is considered of interest to study the microbiological characteristics and the susceptibility patterns of Rhodotorula isolated from clinical samples. A total of 35 different strains of Rhodotorula were studied. In vitro susceptibility testing to 5-fluorocytosine, amphotericin B, ketoconazole, fluconazole and itraconazole was performed. All the strains were considered sensitive to 5-fluorocytosine, amphotericin B, ketoconazole and itraconazole and resistant to fluconazole. As a conclusion, we can state that all the antifungal agents tested, except fluconazole, are useful medicaments for the treatment of infections by the Rhodotorula genus. This revised version was published online in June 2006 with corrections to the Cover Date.     

In Vitro Characterization of Circulating Endothelial Progenitor Cells Isolated from Patients with Acute Coronary Syndrome

Background

The current understanding of the functional characteristics of circulating endothelial progenitor cells (EPC) is limited, especially in patients affected by cardiovascular diseases. In this study, we have analyzed the in vitro clonogenic capacity of circulating EPC, also known as endothelial colony-forming cells (ECFC), in patients with acute coronary syndrome (ACS), in comparison to the colony forming unit-endothelial-like cells (CFU-EC) of hematopoietic/monocytic origin.

Methodology/Principal Findings

By culturing peripheral blood mononuclear cells (PBMC) of patients with ACS (n = 70), CFU-EC were frequently isolated (from 77% of ACS patients), while EPC/ECFC were obtained only in a small subset (13%) of PBMC samples, all harvested between 7–14 days after the acute cardiovascular event. Notably, ex-vivo generation of EPC/ECFC was correlated to a higher in vitro release of PDGF-AA by the corresponding ACS patient PBMC. By using specific endothelial culture media, EPC/ECFC displayed in vitro expansion capacity, allowing the phenotypic and functional characterization of the cells. Indeed, after expansion, EPC/ECFC exhibited a normal diploid chromosomal setting by FISH analysis and an immunophenotype characterized by: i) uniform positivity for the expression of CD105, CD31, CD146 and Factor VIII, i) variable expression of the CD34, CD106 and CD184 markers, and iii) negativity for CD45, CD90, CD117 and CD133. Of interest, in single-cell replanting assays EPC/ECFC exhibited clonogenic expansion capacity, forming secondary colonies characterized by variable proliferation capacities.

Conclusion/Significance

Our data indicate that a careful characterization of true EPC is needed in order to design future studies in the clinical autologous setting of patients with ACS.     

Isolation, characterization and molecular cloning of a lipolytic enzyme secreted from Malassezia pachydermatis

Lipophilic Malassezia species may induce catheter-associated sepsis in premature neonates and immunocompromised patients receiving parenteral lipid emulsions. To assess the participation of lipolytic enzymes in the pathogenesis of this yeast, we cloned a gene encoding the enzyme. A lipolytic enzyme in the culture supernatant of Malassezia pachydermatis was purified 210-fold to homogeneity. The enzyme showed high esterase activity toward p-nitrophenyl octanoate. The cDNA encoding the enzyme was cloned using a degenerate oligonucleotide primer constructed from the N-terminal amino acid sequence. The cDNA consisted of 1582 bp, including an open reading frame encoding 470 amino acids. The first 19 amino acids and the following 13 amino-acid sequence were predicted to be the signal peptides for secretion and prosequence, respectively. The predicted molecular mass of the 438-amino acid mature protein was 48 kDa. Analysis of the deduced amino acid sequence revealed that it contains the consensus motif (Gly-X-Ser-X-Gly), which is conserved among lipolytic enzymes. Homology investigations showed that the enzyme has similarities principally with 11 lipases produced by Candida albicans (29-34% identity) and some other yeast lipases.